How to fix spotlight search on a macOS

Important: We have a current backup of your Mac.

Open Terminal:

Now type in the following commands into Terminal, in the exact order they are shown:

sudo mdutil -i off /
sudo mdutil -i on /
sudo mdutil -E /

The first command turns spotlight off
The second command turns spotlight back on
The final command restarts the spotlight index.
If, after a few minutes, spotlight is still not indexing, try running this command, followed by the three commands above:

sudo rm -rf /.Spotlight-V100